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I finally got my BMW scanner and hooked it up last night to see why my airbag light is on. I got two errors using PA Soft, 50 Power Supply Undervoltage, and F0 Internal Control Unit Fault. These codes won't clear. I also got a power supply code for the radio antenna, which came back after clearing it.

After some researching it seems that the SRS module might need to be replaced and/or my charging/battery system is dying. My alternator has never been replaced and my battery is getting pretty old, so no matter what I have to check these. I'm not sure what this power supply error for my radio antenna means, but it makes me suspect as well. The only other culprit I came across could be the battery safety terminal, although the airbag light only recently came on and my car has not been hit recently, nor hit hard enough for any airbags to deploy since I've owned it. Aside from testing the charging system and battery does anyone have any ideas on how to diagnose this without throwing a few hundred dollars in parts at it? I haven't seen this combo of errors yet.

This is the problem when you get too many complex tools in the hands of novices.

1. Your screen shots using BMW Scanner 1.4.0 shows no active faults. So therefore you should NOT have an aibag light on. All Active Faults should show up as RED.

2. You have a number of items showing power supply or low Voltage. You need to look into this before you get too excited. See the 3rd link in my signature and bring up the battery/charging Voltage on your dash. Get to AutoZone, Advance, Pep Boys and get your battery checked.

3. You can get real time data for the airbag/SRS system and see seat belts latched, seat sensors being activated and so forth.

4. You may have in intermittent connection problem to an airbag. You need to log the date & mileage of all faults, clear them and watch for when any indicator lights come on. Then try to scan for the issue IMMEDIATELY.

5. Also to add you cannot clear a code that is not active, your codes/errors are not active, so they will not clear with software. Also an active fault cannot be cleared (or at least permanently) if the fault condition is still present, the fault needs to be corrected before you can clear the code(s). Sometimes you can clear the fault and the fault will come back immediately, sometimes it take a bit for the polling cycles to be completed.

You will likely start to see a trend and you may get more info. Error codes are nothing more than clues, you cannot take what they state as gospel and knee jerk to replace parts, you car and your wallet will not appreciate it.

I agree I'm a novice with this software, granted I've only used it for a matter of an hour maybe. The fact is that my airbag light IS on. I thought that these codes which show "fault not currently present" wouldn't matter, but they are the only SRS errors so I'm at a loss as to how the software works here. The real time data shows every sensor working properly for the SRS.

As for knee jerks to replace things, that's exactly what I don't want to do, hence making this thread. Other than the "clear errors" button, is there something I'm missing on how to reset the airbag light with PA Soft? If I click to clear the errors the airbag light never goes off, not even for a moment.

Checking the charging system I can do myself when I have some free time.

If the real time data show everything working correctly, then my suggestion is to shut the car down and disconnect the battery for 5 minutes, then touch the battery cables together for about 30 seconds to drain the power from the rest of the modules.

Note, when you touch the battery cables together, your batter is disconnected!! Just to make sure it is clear what you are doing.

Just some history.

How long have you owned the car?

Have you always had the SRS light on? m

Do you think the SRS module is original?

Do you think any of he airbags have ever been deployed??

You may need to pull your module and send it to one of the online airbag controller reset companies?? They usually charge about $60-$80 as I recall to reset any crash data that the module may have recorded??

I'll give disconnecting the battery a try and see if I can clear it. I find it a little strange that the light will not go off at all using PA Soft. I figured it would probably go off for a minute and come right back at the least.

As for history I've owned the car for 6 years, bought it with 45k miles and as far as I know the airbags were not deployed in the 45k miles before I owned it. The light has been on for probably a couple of months now, but before that I've never had it come on. Nothing obvious happened to cause it, just popped on one day. As far as I know the control module is original.

Ok, tried disconnecting the battery and both errors are still there as is the light, however the internal control unit fault is now "currently present" in red. The errors still won't clear and the light won't turn off. After disconnecting the battery and starting the car the light was off for a half a second and then came back on. Leaning towards the control module now, battery is only two years old but I haven't tested it or the charging system.

Id replace the module with a used one. Yours has a fault. I went through the same thing. Try creating new errors by unplugging the seat and see if you can clear them. If you cant, id suspect a bad module.

What I am saying is you really need to try and read/extract/suck the current programming out of the existing module if possible.

The OP can actually use his software to do this assuming he can properly communicate with his replacement module. Also suggest before he programs a replacement module that he try to read/extract/suck the programming info and store it. You can actually jump back and forth between programs if needed and if you have them store.. He can also likely look at his software to determine how many options and features can be programmed into an airbag module.

At times you may be lucky and end up with a module out of a like model and year that has the same profile, but it is just as likely that you could possibly end up with a module that has different programming.

Just because there is no airbag light if you put a used module in a car does not mean the module is configured properly.

Also there are potential big liability issues as well. These module store crash data and airbag deployment info. If you buy a used module on ebay, has any existing crash data been cleared? Does it have history for some other event in some other car?

Just saying you need to be careful how you handle airbag modules, they are not just plug & play.

I have not paid close attention to the E46 configuration, however, the E39 had the rear airbags disabled in certain years. This was entirely configurable with software within the same module.

Just saying that the OP needs to be aware of what he is doing to protect himself and his occupants.

What I am saying is you really need to try and read/extract/suck the current programming out of the existing module if possible.

The OP can actually use his software to do this assuming he can properly communicate with his replacement module. Also suggest before he programs a replacement module that he try to read/extract/suck the programming info and store it. You can actually jump back and forth between programs if needed and if you have them store.. He can also likely look at his software to determine how many options and features can be programmed into an airbag module.

At times you may be lucky and end up with a module out of a like model and year that has the same profile, but it is just as likely that you could possibly end up with a module that has different programming.

Just because there is no airbag light if you put a used module in a car does not mean the module is configured properly.

Also there are potential big liability issues as well. These module store crash data and airbag deployment info. If you buy a used module on ebay, has any existing crash data been cleared? Does it have history for some other event in some other car?

Just saying you need to be careful how you handle airbag modules, they are not just plug & play.

I have not paid close attention to the E46 configuration, however, the E39 had the rear airbags disabled in certain years. This was entirely configurable with software within the same module.

Just saying that the OP needs to be aware of what he is doing to protect himself and his occupants.

Thats fine, i plan on getting mine checked when i go to the dealer. You can have the airbags in the rears disabled at the dealership for child seats etc. If you installing a used module you will not know wither the previous car had this done. From calling several salvage yards and getting the part numbers from different cars it seems there are part number differences between the models (sedan and coupe) and wither or not the car has side airbags.

It seems other then that they have the same programing. Take it with a grain of salt. For the vary reason that the rear bags can be disabled it is good to go and get the module checked at the dealership. Im just giving info i found while trying to fix a similar issue on my recently purchased e46...

Just for my own knowledge do you mind letting me know the year and model and SRS options for your car so i can see if coincides with my previous findings of part numbers?

As a quick module diagnosis what i did was unhook the passenger seat connector with the battery disconnected. Upon reconnecting the battery this should give you several codes (tensioner, occupancy sensor, etc.) Disconnect the battery again and reconnect the connector. Then try to read the new codes. You should be able to read these codes. However, i was able to read code but not clear. I bought a used module and connected it. There were quite a few codes when i hooked it up. Then i cleared the codes and there was no more SRS light.

By creating a light and fixing the issue i diagnosed that the module was bad and the other codes that would not clear were old faults not clearing and not a current problem. If you still have a fault and you clear the code it will come right back on.

I am a little worried about the programming of a used module. I'm not completely convinced that if all of the numbers match it will be plug and play, although in my search I've come across several different part numbers for e46 cars. I don't believe mine has rear airbags, but does have side airbags. Mine has the following numbers 0 285 001 458 and 65.77 - 6912755

I've seen this part number also listed for my car 0 285 001 368 which makes me think the number might be specific not only for my model and year but also for the specific airbag configuration.